<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>类选择器</title>
		<style>
			.center {
				text-align: center;
				color: red;
			}
		</style>
	</head>
	<body>
		<h1 class="center">居中的红色标题</h1>
		<p class="center">居中的红色段落。</p>
	</body>
</html>
